The present invention generally relates to sustained-release pharmaceutical granular preparations. Particularly, it is concerned with such preparations that effectively control the dissolving and/or absorption rates of pharmacologically-active ingredients which are otherwise liable to be decomposed with the gastric juice and/or rapidly absorbed into the living body to raise the concentration in the blood to a dangerous extent.
Certain kinds of pharmacologically active substances, particularly weakly basic ones including their acid addition salts, are rapidly dissolved in the stomach and therefore the blood (serum and/or plasma) levels of the substances are correspondingly rapidly raised.
On the other hand, it is desirable to raise the serum and/or plasma level of a pharmacologically active substance rapidly up to a predetermined level and subsequently maintain the level for a period of time as long as possible.
In the cases of, for instance, antihypertensive agents and hypoglycemic agents, a rapid rise in the serum and/or plasma levels of such agents up to an unexpected degree is a sign of danger for a patient who is given the agent. Accordingly, it is desirable to properly control the rise in the level of the active ingredients.